Golf club shaft

ABSTRACT

A round, substantially uniform diameter tubular golf club shaft of simplified configuration, having interchangeable butt and tip ends, either of said ends adapted to fit and directly attach to the external surface of a standard female hosel of a golf clubhead or to fit and directly attach to a standard golf club grip.

BACKGROUND OF THE INVENTION

[0001] This invention relates to golf clubs, and, in particular, a golf shaft of substantially simplified cylindrical configuration which reduces manufacturing costs of the shaft without incurring negative ancillary costs for the golf club.

[0002] Heretofore, golf shafts have been made in a tapered shape, with the tip or club head end being of smallest diameter and the butt or grip end being of the largest diameter. The purpose of this construction was to increase shaft flexibility in the tip end for proper whip and feel. The expanding taper from tip to butt was usually in the form of a smooth taper or in the form of a series of steps of increasing diameter. For metal shafts, the stepped taper design is most common and requires a series of dies of different diameters to shape the steps. Also, separate cold-drawing operations are required for each step. This process is lengthy and costly.

[0003] Composite shafts are generally made by wrapping laminations of fiber plies, impregnated with uncured epoxy, onto a mandrel and subsequently heat cured. The mandrel must be precisely machined to the desired shaft taper. The laminations are necessarily cut into irregular trapezoidal shapes called “flags.” This process is also lengthy and costly.

[0004] By replacing the usual tapered shape of a golf shaft with a cylindrical shape, very many tooling dies and manufacturing steps are eliminated, since only a single draw is necessary for a metal shaft or a simple cylindrical mandrel rod for wrapping a composite shaft. For the latter, only rectangular pre-preg tape would be required rather than complex trapezoidal “flags.” Composite cylindrical shafts could also be made by the quicker and more efficient pultrusion process rather than the tedious hand wrapping process.

[0005] A study of prior art shows attempts having been made to simplify the form of the golf shaft from a taper to a straight cylinder. The Billings cylindrical shaft construction of U.S. Pat. No. 5,547,189, although perhaps effective for use in a putter, is unsuited for use in golf irons or woods which are swung at high velocity. The extremely large shaft diameter of 0.75 to 1.50 inches increases aerodynamic drag which decreases the golf club swingspeed, leading to loss of distance. Also, the transverse geometrical moment of inertia of this shaft is excessive, reducing its flex and torque (twist) to such a degree, that the golf club would feel too stiff and “boardlike.” Finally, this shaft requires clubheads with very large, nonstandard hosels as well as very large nonstandard grips. This not only increases manufacturing expense but the resultant overall weight increase in the golf club, along with the unusual swingweight imbalances caused by the heavy hosel and grip, lead to slower swingspeeds and loss of distance.

[0006] The Ishizuka Patent No. 5,885,169 also depicts a cylindrical golf shaft which lends itself to lower manufacturing costs. However, overall savings in the manufacture of a golf club utilizing this shaft are not achieved due to the fact that special clubheads with enlarged female hosels are required. In addition, the enlarged, more weighty hosel moves the center of gravity or “sweetspot” of the golf clubhead upwards and inwards towards the hosel, detracting from the efficiency of the clubhead. Loss of distance and accuracy result.

SUMMARY OF THE INVENTION

[0007] It is the purpose of the present invention to provide a golf club shaft of substantially cylindrical construction to effect cost savings in the manufacture thereof, and without incurring negative compensating costs for nonstandard grips or clubheads and without reducing the functional effectiveness of the golf club. This goal is achieved by attaching the internal surface of the unconventionally large shaft tip of the present invention to the outside hosel surface, rather than the inside socket of a standard clubhead. The resultant outside diameter of the inventive shaft can be made to fall within the range of standard grip sizes.

[0008] Thus, since standard clubheads and standard grips are used in conjunction with the inventive shaft, cost savings are realized in the construction of the golf club in its entirety, and this without negative distortions in the functional efficiency of the clubhead, grip, or club.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] These and other advantages will become apparent in the course of the specification, reference being had to the accompanying drawings forming a part thereof, wherein like numerals refer to like parts throughout and in which:

[0010]FIG. 1 is a side elevational view of the golf shaft of the present invention, installed in a golf club;

[0011]FIG. 2 is a cross sectional view of the golf shaft, taken on transverse section line 2-2 of FIG. 1;

[0012]FIG. 3 is a central fragmentary cross sectional view of the shaft end, taken on line 3-3 of FIG. 1;

[0013]FIG. 3A is a central fragmentary cross sectional view of an alternate shaft end;

[0014]FIG. 3B is a central fragmentary cross sectional view of a second alternate shaft end.

DETAILED DESCRIPTION OF THE INVENTION

[0015] Referring to FIG. 1, the golf shaft of the present invention, designated as an entity by the numeral 10, consists of a hollow, cylindrical tube of uniform outside and inside diameters for the substantial length of the shaft. It extends from its lower tip end 14, attached to hosel 16 of golf clubhead 28, to its upper butt end 12, to which standard grip 24 is attached. It must be realized however, that in its blank or raw form, either end of golf shaft 10 may be considered and used as the tip end.

[0016] The preponderantly uniform inside diameter d and the outside diameter D of golf shaft 10 is shown in FIG. 2. FIG. 3 illustrates in detail the novel way in which golf shaft 10 is attached, with its inside surface 26 bonded to the outside surface 16 of a standard female clubhead hosel by means of epoxy adhesive 20. This is in contrast to the conventional method of attaching the small tip section of a standard tapered golf shaft 22 (shown in phantom) to the inside surface of socket 18 of the standard female clubhead hosel 16, as shown in FIG. 1. Dimension C represents bonding length for attaching golf shaft 10 to clubhead hosel 16 and is generally around 25 to 45 mm.

[0017] Since female clubhead hosels are not of a standard outside diameter, but can vary over a range of 0.5 mm, generally from 13 to 13.5 mm for iron clubheads and 12 to 12.5 mm for metalwood clubheads, it may be necessary to slightly increase the inside connecting tip end 14 of golf shaft 10 to diameter d1 as shown in FIG. 3A. On the other hand, it may be necessary to slightly decrease the inside diameter of connecting tip end 14 to diameter d2 as shown in FIG. 3B. In either case, the change in inside tip diameter is an almost imperceptible 0.25 mm.

[0018] To sum up, golf shaft 10 may be made with constant inside and outside diameters, d and D respectively, throughout its entire length or, for the sake of versatility of fit, it can have larger inside diameter d1 at one connecting end and diameter d at the other end, or smaller inside diameter d2 at one end and inside diameter d at the other end, or diameter d1 at one end and diameter d2 at the other. With this method, it is possible to fit shaft 10 to the external surface of the vast majority of female clubhead hosels.

[0019] The golf clubmaker needs only to attach the better fitting end of golf shaft 10 to the golf clubhead hosel 16, and trim the opposite end to length. Only one cut is necessary. Most present day tapered golf shafts require a cut at the small tip end to adjust its flex and a second cut at its butt end to adjust club length. The outside butt diameter of standard golf shafts generally vary from 14.7 mm to 15.7 mm for both iron shafts and wood shafts. These dimensions correspond to inside dimensions of standard golf grips. By subtracting the maximum hosel outside diameter for an iron clubhead (13.5 mm) from the outside diameters listed above, we deduce a wall thickness range for the golf shaft 10 of 1.2 mm/2 to 2.2 mm/2 or 0.6 mm to 1.1 mm. These wall thicknesses are sufficient to provide necessary strength and performance for golf shaft 10, when a proper material is used in its construction.

[0020] Since the inside diameter of shaft 10 is dictated by the outside diameter Dh of the female hosel 16 of standard clubhead 28, and the outside diameter of shaft 10 is dictated by the inside diameter of standard golf grip 24, the flexural strength and feel of golf shaft 10 must necessarily be controlled by the modulus of elasticity and wall thickness, t, of the material chosen for the shaft. Shaft 10 can be made of any metal, metal alloy, or fiber/resin composite known to the art. With a vast choice of materials available for the construction of golf shaft 10, it is possible to choose many that render acceptable feel, performance and durability when configured in accordance with the geometrical parameters of golf shaft 10 of the present invention. Scandium/aluminum alloy is just one material that I have found to fulfill all requirements. A mixed composite of fiberglass, graphite and resin also performs acceptably well.

[0021] The extreme reduction in complexity and expense of manufacturing the constant diameter golf shaft 10 of the present invention versus a tapered shaft, and its capacity to readily assemble to the external surface of a standard female clubhead hosel, and to standard grips, with no adapters nor modifications of the clubhead or grip being required and its ability to perform as well as a conventional tapered shaft, constitutes the basis for which the novelty of the present invention is predicated. 

What I claim as new is as follows:
 1. A hollow, cylindrical golf club shaft of uniform outside and inside diameters throughout the substantial portion of its length, having a slight local increase or decrease of approximately 0.25 mm in inside diameter at at least one end for a length of approximately 25 to 45 mm, said shaft being adapted for fitting of a standard golf club grip at either end and adapted for fitting of its internal surface at either end to the external surface of a standard female golf clubhead hosel.
 2. A hollow, cylindrical golf club shaft of uniform outside and inside diameters throughout its length, said shaft being adapted for fitting of a standard golf club grip at either end and adapted for fitting of its internal surface at either end to the external surface of a standard female golf clubhead hosel. 